MasteringCherristry: Actvity 4-Heats of Comustion Google Chrome Secure httpsfise
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MasteringCherristry: Actvity 4-Heats of Comustion Google Chrome Secure httpsfisession.masteringchemistry.com myct itemView?assignmentProblemD Activity 4-Heats of ComtinCh5: Heats of Combustion. Seg3: Hess's Law 90691841 previous 3 of 3 |return to assignment Ch5: Heats of Combustion. Seg3: Hess's Law Calculating Reaction Enthalpies Using Hess's Law Follow the steps below and use the information provided on the left to find the Hran for the following process: Enthalpy (H) Is a state function, which means the enthalpy of a given chemical reaction is independent of the path taken from the initial to final states for that chemical reaction Enthalpy Change (AH) is a measure of the energy change of a system that does virtually no work. A 11 value written at the end of a balanced equation represents the heat change that occurs when th quantities reacting are equal to the coefficients in the balanced equation. Enthalpy of Reaction (AHIs equal to the heat galned or lost by the reaction at constant pressure. Hrzn-greaction (at constant pre88ure) Overall Reaction :2D > A12B Hrn ?k/ Given: Reaction 1: Reaction 2: D A+2B 2C 112=10.0 kJ The questions that follow will have you manipulate Reactions 1 and 2 so that the sum of the individual reactions will result in the overall reacticn. when you multiply an entire reaction by a number, you must also multiply by the same number Hess's Law states that if a reactian process takes place in a series of steps, the enthalpy of reaction. 'za, will equal the sum of the enthalpy changes for the individual steps in that reaction procoss. when you reverse an entire reaction, you must also change the sign of Part A Comparing Reaction 1 to the overall reaction The overall reaction has two times the moles of D in the balanced equation. This means that Reection 1 will have to be doubled to achieve the overall reaction. What is the (new) H, once you have double Reaction ? The ariount of heat released or abscrbed depends directly on the amount of substance that reacts, therefore, H is an extensive property (i.e. the 11 value for 2 moles of a substance will be twice the H value for 1 mole of the substance), (new Reaction 1: 2D 2C (new) kJ Submit My Answers Give Un If the reaction is run in reverse, the sign , but riot the magnitude, of H will change (ie, if a reaction releases a certain quantity of heat, it will absorb the same amount of heat if the reverse reaclion were to occur). Part B Comparing Reaction 2 to the overall reaction The overall reaction has B as a product. This means that Reaction 2 would have to be reversed to achieve the overall reaction, what is the (new) H2 once you have reversed Reaction 27 (new) Reaction 2 : 2C A+2B (new) kJ = Submit My Answers Give Un 6:47 PM Type here to searchExplanation / Answer
C)
Reaction requires: 2 mol of D, cancel mol of C
the best way to do this is via addition
Rxn 1 + Rxn2
2D + 2C = 2C + A + 2B H = 4 - 10
2D = A + 2B H = - 6
answer is -6 kJ
D)
Balance
CH4 + O2 = CO2+ H2O
balance C, then H finally O
CH4 + O2 = CO2+ 2H2O
balance O
CH4 + 2O2 = CO2+ 2H2O